mc68hc11ea9 Freescale Semiconductor, Inc, mc68hc11ea9 Datasheet - Page 31

• Manufacturer Part Number: mc68hc11ea9
• Description: 8-bit Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

7 Timing System
MC68HC11EA9
MC68HC11EA9TS/D
The timing system is based on a free-running 16-bit counter with a four-stage programmable prescaler.
A timer overflow function allows software to extend the system’s timing capability beyond the counter's
16-bit range. The main timer consists of the timer prescaler, the 16-bit free-running counter, and the
capture/compare unit. 7.2 Main Timer details this portion of the timing system.
The free-running counter can be driven by either the EXTAL signal, as in other M68HC11 derivatives
or it can be driven by a software-controlled phase-locked loop (PLL) frequency synthesizer which has
been added to the MC68HC(7)11EA9 MCUs. The PLL allows the MCU to operate in WAIT mode with
extremely low power requirements. Refer to 7.1 Phase-Locked Loop Synthesizer.
In addition, the timing system includes pulse accumulator and real-time interrupt (RTI) functions, as well
as a clock monitor function, which can be used to detect clock failures that are not detected by the COP
system. Refer to the appropriate paragraphs within this section for information regarding these func-
tions. Table 12 shows a summary of the crystal-related frequencies and periods.
Time-out Tolerance
Control Bits
(–0 ms/+...)
RTR[1:0]
PR[1:0]
CR[1:0]
0 0
0 1
1 0
1 1
0 0
0 1
1 0
1 1
0 0
0 1
1 0
1 1
overflow —
overflow —
overflow —
overflow —
1 count —
1 count —
1 count —
1 count —
Freescale Semiconductor, Inc.
131.072 ms
524.288 ms
COP Watchdog Timeout Rates (Period Length)
65.536 ms
262.14 ms
524.28 ms
16.384 ms
32.768 ms
65.536 ms
32.768 ms
Periodic (RTI) Interrupt Rates (Period Length)
8.192 ms
4.0 MHz
1.0 MHz
1000 ns
32.8 ms
16.0 s
1.049 s
2.098 s
For More Information On This Product,
4.0 s
8.0 s
Main Timer Count Rate (Period Length)
Common System Frequencies
Go to: www.freescale.com
Table 12 Timer Summary
32.768 ms
131.07 ms
262.14 ms
524.29 ms
16.384 ms
32.768 ms
16.384 ms
65.536 ms
262.14 ms
4.096 ms
8.192 ms
8.0 MHz
2.0 MHz
16.4 ms
1.049 s
500 ns
2.0 s
4.0 s
8.0 s
21.845 ms
32.768 ms
174.76 ms
349.52 ms
10.923 ms
21.845 ms
10.923 ms
43.691 ms
174.76 ms
699.05 ms
12.0 MHz
2.731 ms
5.461 ms
1.333 s
2.667 s
5.333 s
3.0 MHz
10.9 ms
333 ns
Definition
XTAL
2
2
2
2
2
2
2
2
2
2
2
2
2
16/E
1/E
4/E
8/E
16
18
19
20
13
14
15
16
15
17
19
21
15
E
/E
/E
/E
/E
/E
/E
/E
/E
/E
/E
/E
/E
/E
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